Acoustic MEMS sensors, such as e.g. MEMS microphones, are open components and exposed to the surrounding environment in a manner governed by their function. Therefore, such sensors are perceptible to contaminants or contaminations with organic or inorganic particles, liquids, moisture, etc., which can penetrate into the active sensor structures. This can lead to a malfunction or to a reduced performance of the sensor. Cellular phone manufacturers invest great efforts to protect the sensors within the application, such as e.g. within mobile devices, by means of complex grilles and special ports.
Furthermore, it should be noted that MEMS sensors are not protected at all during component assembly, and so possible contaminations within the production line can also cause malfunctions. Consequently, cost-intensive clean room arrangements are required in order to prevent as far as possible impairments that otherwise occur in the production yield.
As has already been discussed above, MEMS microphones are protected for example in part by mechanical protection elements, such as grilles, etc., at the component level. This is costly and often restricts product design at the end customer level.
By contrast, approaches for the design of the capacitive structure also exist at the level of the microphone components. The capacitive structure has for example a perforated back plate, a deflectable membrane and the intervening air gap, wherein for example the sensitive and active sensor capacitance, i.e. the air gap, is protected by the membrane. Depending on the desired housing design for the microphone, however, the resulting design of the microphone also has to be adapted if the desired protective effect is intended to be obtained for example depending on the positioning with respect to the sound port (sound opening). Furthermore, the MEMS microphone design is intended not to impair the acoustic behavior of the microphone, that is to say that it is desirable to obtain the highest possible signal-to-noise ratio (SNR) of the microphone output signal.